Search

A combinatorial library of twenty-three, phase pure, near-NMC111 (LiNi0·33Mn0·33Co0·33O2) compositions were synthesised and their electrochemical performance, was mapped (in lithium ion half-cells). Each of the 23 compositions was made in series, using a two-step process of 1) a rapid initial continuous hydrothermal precipitation, followed by 2) solid state lithiation. The 23 lithiated NMC samples were then subjected to analytical methods including electron microscopy (selected samples), Powder X-ray Diffraction and electrochemical tests in half cell Li-ion configurations versus Li metal. A sample with a Ni:Mn:Co (NMC) ratio of 39:28:33, revealed a specific capacity of 150 mA h g−1 at a C/20 rate, which was 63 and 43% greater capacity than NMC111 and NMC433 samples produced in this work, respectively. The sample with NMC ratio 47:25:28, showed the best capacity retention characteristics, retaining 70% of its C/20 capacity at 1C, after 40 cycles. Further analysis of all the samples by cyclic voltammetry and electrochemical impedance spectroscopy, allowed compositional mapping of diffusion coefficients. Overall, the mapping data revealed a gradual change of properties across compositional space, which has validated our combinatorial approach and allowed identification of the optimum performing near-NMC111 cathode materials.

Major structural differences in lithium nickel manganese cobalt oxides (NMC) prepared under identical conditions have been uncovered using neutron powder diffraction. Sample NMC-622 was obtained as a single Rm crystal structure with little defects, whereas NMC-811 showed significant Li deficiency and NMC-433 formed three distinct phases; ordered Rm, disordered Rm and a C2/m phase. Local diffusion behaviour was also studied by muon spin relaxation (μSR). It was observed that single phase Rm NMC-622 showed a higher lithium diffusion coefficient (4.4 × 10−11 cm2 s−1) compared to lithium deficient NMC-811 (2.9 × 10−11 cm2 s−1), or the highly disordered NMC-433 (3.4 × 10−11 cm2 s−1). Furthermore, activation energies for the Li diffusion process were estimated to be 58 meV, 61 meV and 28 meV for NMC-811, NMC-622 and NMC-433, respectively.

Synchrotron X-ray diffraction computed tomography (XRD-CT) was employed to study a commercial 18650 cylindrical LiNi0.8Co0.15Al0.5O2 (NCA) battery under operating conditions and during seven cycles. Multiple chemical heterogeneities related to the lithium distribution were observed in both the cathode and the anode from the analysis of the spatially-resolved diffraction signals. It is shown that during the battery charging, the anode exhibits different degrees of activity regarding the lithiation process. Explicitly, the following three regions were identified: uniform/homogenous lithiation, delayed lithiation and inactive-to-lithiation regions. The inactive-to-lithiation anode region was a result of the specific cell geometry (i.e. due to lack of cathode tape opposite these anode areas) and throughout the cycling experiments remained present in the form of LiC30-30+. The delayed lithiation region was seen to have a direct impact on the properties of NCA in its close proximity during the battery discharging, preventing its full lithiation. Further to this, the aluminum tab negatively affected the NCA in direct contact with it, leading to different lattice parameter a and c evolution compared to the rest of the cathode.

A library of 66 perovskite BaxSryCazTiO3 (x + y + z = 1) samples (ca. three grams per sample) was made in ca. 14 h using a high-throughput continuous hydrothermal flow synthesis system. The as-synthesized samples were collected from the outlet of the process and then cleaned and freeze-dried before being evaluated individually as oxygen reduction catalysts using a rotating disk electrode testing technique. To establish any correlations between physical and electrochemical characterization data, the as-synthesized samples were investigated using analytical methods including BET surface area, powder X-ray diffraction (PXRD) and in selected cases, transmission electron microscopy (TEM). The aforementioned approach was validated as being able to quickly identify oxygen reduction catalysts from new libraries of electrocatalysts.

It has been shown that the introduction of several transition metal (TM) dopants into SnO2 lithium‐ion battery anodes can overcome the issues associated with the irreversible capacity loss from the conversion reaction of SnO2 and the aggregation of the metallic Sn particles formed upon lithiation. As the choice of the single dopant, however, plays a decisive role for the achievable energy density – precisely its redox potential – we investigate herein TM co‐doped SnO2, prepared by using a readily scalable continuous hydrothermal flow synthesis (CHFS) process, to tailor the dis‐/charge profile and by this the energy density. It is shown that the judicious choice of different elemental doping combinations in samples made via CHFS simultaneously improves the cycling performance and the full‐cell energy density. To support these findings, we realized a lithium‐ion full‐cell incorporating the best performing co‐doped SnO2 as negative electrode and high‐voltage LiNi0.5Mn1.5O4 (LNMO) as positive electrode–to the best of our knowledge, the first full‐cell based on such anode material in combination with LNMO as cathode active material.

Experimental evidence for the presence of two computationally theorised diffusion pathways, namely the oxygen dumbbell hop (ODH) and tetrahedral site hop (TSH), has been given for the first time by muon spin relaxation (µSR) on sub-stoichiometric LixNi0.77Co0.14Al0.09O2. µSR has proven to be a powerful tool that is able to discriminate between diffusion pathways that occur on different timescales on a local level, where bulk electrochemical techniques cannot. Whereas the estimated values of DLi at lithium concentrations of 0.87 and 0.71 were found to be on the order of 10−11 by electrochemical impedance spectroscopy, contributions to diffusion from ODH and TSH were determined to be on the order of 10−11 and 10−10 cm2 s−1, and a factor of four decrease in Ea for both samples, in excellent agreement with theoretical calculations on related compounds. Rietveld refinement of both X-ray and neutron diffraction data was also used to interrogate the local structure of the materials where no contribution from Li+/Ni2+ cation mixing was observed.

Chromium oxides with the spinel structure have been predicted to be promising high voltage cathode materials in magnesium batteries. Perennial challenges involving the mobility of Mg2+ and reaction kinetics can be circumvented by nano-sizing the materials in order to reduce diffusion distances, and by using elevated temperatures to overcome activation energy barriers. Herein, ordered 7 nm crystals of spinel-type MgCr2O4 were synthesized by a conventional batch hydrothermal method. In comparison, the relatively underexplored Continuous Hydrothermal Flow Synthesis (CHFS) method was used to make highly defective sub-5 nm MgCr2O4 crystals. When these materials were made into electrodes, they were shown to possess markedly different electrochemical behavior in a Mg2+ ionic liquid electrolyte, at moderate temperature (110 °C). The anodic activity of the ordered nanocrystals was attributed to surface reactions, most likely involving the electrolyte. In contrast, evidence was gathered regarding the reversible bulk deintercalation of Mg2+ from the nanocrystals made by CHFS. This work highlights the impact on electrochemical behavior of a precise control of size and crystal structure of MgCr2O4. It advances the understanding and design of new cathode materials for Mg-based batteries.

Sodium titanate nanopowder (nominal formula Na1.5H0.5Ti3O7) was directly synthesized using a continuous hydrothermal flow synthesis process using a relatively low base concentration (4 M NaOH) in process. The as-made titanate nanomaterials were characterised using powder X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, Brunauer–Emmett–Teller analysis and transmission electron microscopy, and evaluated as potential electrode materials for Li-ion and Na-ion batteries. Cyclic voltammetry studies on half-cells revealed that the sodium titanate nanomaterial stored charge primarily through a combination of pseudocapacitive and diffusion-limited processes in both systems. Electrochemical cycling tests at a high specific current of 1000 mA g−1, revealed that the Li-ion and Na-ion cells retained relatively high specific capacities after 400 cycles of 131 and 87 mAh g−1, respectively. This study demonstrates the potential of CHFS-made sodium titanate nanopower as an anode material for both Li- and Na-ion cell chemistries.

A library of 66 perovskite Ba

Developing large-scale and high-performance OER (oxygen evolution reaction) and ORR (oxygen reduction reaction) catalysts have been a challenge for commercializing secondary zinc–air batteries. In this work, transition metal-doped cobalt–nickel sulfide spinels are directly produced via a continuous hydrothermal flow synthesis (CHFS) approach. The nanosized cobalt–nickel sulfides are doped with Ag, Fe, Mn, Cr, V, and Ti and evaluated as bifunctional OER and ORR catalyst for Zn–air battery application. Among the doped spinel catalysts, Mn-doped cobalt–nickel sulfides (Ni1.29Co1.49Mn0.22S4) exhibit the most promising OER and ORR performance, showing an ORR onset potential of 0.9 V vs. RHE and an OER overpotential of 348 mV measured at 10 mA cm−2, which is attributed to their high surface area, electronic structure of the dopant species, and the synergistic coupling of the dopant species with the active host cations. The dopant ions primarily alter the host cation composition, with the Mn(III) cation linked to the introduction of active sites by its favourable electronic structure. A power density of 75 mW cm−2 is achieved at a current density of 140 mA cm−2 for the zinc–air battery using the manganese-doped catalyst, a 12% improvement over the undoped cobalt–nickel sulfide and superior to that of the battery with a commercial RuO2 catalyst.

The Li+ ion diffusion characteristics of V- and Nb-doped LiFePO4 were examined with respect to undoped LiFePO4 using muon spectroscopy (µSR) as a local probe. As little difference in diffusion coefficient between the pure and doped samples was observed, offering DLi values in the range 1.8–2.3 × 10−10 cm2 s−1, this implied the improvement in electrochemical performance observed within doped LiFePO4 was not a result of increased local Li+ diffusion. This unexpected observation was made possible with the µSR technique, which can measure Li+ self-diffusion within LiFePO4, and therefore negated the effect of the LiFePO4 two-phase delithiation mechanism, which has previously prevented accurate Li+ diffusion comparison between the doped and undoped materials. Therefore, the authors suggest that µSR is an excellent technique for analysing materials on a local scale to elucidate the effects of dopants on solid-state diffusion behaviour.

Small methods 5(9), 2100512 - (2021). doi:10.1002/smtd.202100512, Synchrotron high-energy X-ray diffraction computed tomography has been employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2 and C/20. This technique yields maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 × 550 images with 20 × 20 × 3 µm$^3$ voxel size in ca. 1 h). The recently developed Direct Least-Squares Reconstruction algorithm is used to overcome the well-known parallax problem and led to accurate lattice parameter maps for the device cathode. Chemical heterogeneities are revealed at both electrodes and are attributed to uneven Li and current distributions in the cells. It is shown that this technique has the potential to become an invaluable diagnostic tool for real-world commercial batteries and for their characterization under operating conditions, leading to unique insights into “real” battery degradation mechanisms as they occur., Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Nanosized metal germanates (M2GeO4; M = Co, Mn, Zn) were synthesised using a continuous hydrothermal flow synthesis process for the first time. Phase‐pure rhombohedral Zn2GeO4 nanorods, cubic spinel Co2GeO4 nanoparticles, and orthorhombic Mn2GeO4 nanotubes/nanoparticles were obtained. The electrochemical properties of all samples as active materials for negative electrodes in Li‐ion half cells was explored. The galvanostatic and potentiodynamic testing was conducted in the potential range 3.00 to 0.05 V vs. Li/Li+. The results suggest that both alloying and conversion reactions associated with Ge contributed to the stored charge capacity; Zn2GeO4 showed a high specific capacity of 600 mAh g-1 (10 cycles at 0.1 A g -1) due to alloying and conversion reactions for both Ge and Zn. Mn2GeO4 was studied for the first time as a potential negative electrode material in a Li‐ion half‐cell; an excellent specific charge capacity of 510 mAh g-1 (10 cycles / 0.1 A g-1) was obtained with a significant contribution to charge arising from the conversion reaction of Mn to MnO upon delithiation. In contrast, Co2GeO4 only showed a specific capacity of 240 mAh g-1, after 10 cycles at the same current rate, which suggested that cobalt had little or no benefit for enhancing stored charge in the germanate.

Tin oxide-based materials have been intensively investigated as alternative anodes for lithium-ion batteries due to their high specific capacity, environmental friendliness, non-toxicity, and ease of handling.[1] However, the initial formation of Li2O upon lithiation is essentially irreversible, which has a severe effect on the first cycle coulombic efficiency and the reversibly achievable capacity in general.[2] It has been shown that the incorporation of transition metal dopants can address this issue, as it enables the reversible formation and reformation of Li2O.[3] The choice of the dopant, however, plays a critical role for the long-term cycling stability, rate capability, and eventual energy density of the resulting lithium-ion cells.[4] Herein, we show that the addition of specific combination of different dopants allows for further tailoring the electrochemical properties. We also demonstrate the production of such materials using a scalable continuous hydrothermal flow method. The performance of the best composition (Sn0.9Co0.05Mn0.05O2, SCMO) was further improved by applying a carbonaceous coating. The electrochemical investigation of the coated anode material was conducted in half-cells and in high-energy full-cells using high-voltage LiNi0.5Mn1.5O4 (LNMO) as active material for the cathode (Figure 1).[5] The performance of the full-cells was further enhanced by carefully optimizing the anode composition and fine-tuning the full-cell design, considering electrolytes and different pre-lithiation degrees. Reference s : [1] F. Zoller, D. Böhm, T. Bein, D. Fattakhova-Rohlfing, ChemSusChem., 1 2 , 4140 (2019) [2] I.A. Courtney and J.R. Dahn, J Electrochemical Soc., 144 , 2045 (1997) [3] D. Bresser, S. Passerini and B. Scrosati, Energy Environ. Sci. , 9 , 3348 (2016) [4] Y. Ma et al, Sustain. Energy Fuels, 2 , 2601 (2018) [5] A. Birrozzi et al., Batter. Supercaps, 3 , 284 (2020). Figure 1

The Li+ ion diffusion characteristics of V- and Nb-doped LiFePO4 were examined with respect to undoped LiFePO4 using muon spectroscopy (µSR) as a local probe. As little difference in diffusion coefficient between the pure and doped samples was observed, offering DLi values in the range 1.8–2.3 × 10−10 cm2 s−1, this implied the improvement in electrochemical performance observed within doped LiFePO4 was not a result of increased local Li+ diffusion. This unexpected observation was made possible with the µSR technique, which can measure Li+ self-diffusion within LiFePO4, and therefore negated the effect of the LiFePO4 two-phase delithiation mechanism, which has previously prevented accurate Li+ diffusion comparison between the doped and undoped materials. Therefore, the authors suggest that µSR is an excellent technique for analysing materials on a local scale to elucidate the effects of dopants on solid-state diffusion behaviour.

Several nano-sized mixed molybdenum/vanadium oxide monoclinic solid solutions were synthesised using a continuous hydrothermal flow process and studied with a wide range of physical characterization techniques including X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray absorption spectroscopy. The nanomaterials were tested as anodes for Li-ion batteries in the potential range 0.05–3.00 V vs. Li/Li+. Samples with nominal formulas of Mo0.5V0.5O2 and Mo0.33V0.67O2 showed excellent performance, especially at high current rates, due to their highly pseudocapacitive charge storage mechanism. At a specific current of 10 A g−1, Mo0.5V0.5O2 and Mo0.33V0.67O2 showed specific capacities of ca. 200 and 170 mAh g−1, respectively. Mo0.5V0.5O2 also showed good cyclability, with a specific capacity of 480 mAh g−1 after 150 cycles at a specific current of 0.5 A g−1. For cyclic voltammetries conducted at high scan rates, pseudocapacitive charge storage contributed more than 90% to the total charge storage for both samples. The scalability of the synthesis technique and excellent electrochemical performance at high power, make these materials promising as negative electrode active materials for Li-ion batteries.

Lithium-stuffed garnets attract huge attention due to their outstanding potential as solid-state electrolytes for lithium batteries. However, there exists a persistent challenge in the reliable synthesis of these complex functional oxides together with a lack of complete understanding of the lithium-ion diffusion mechanisms in these important materials. Addressing these issues is critical to realizing the application of garnet materials as electrolytes in all solid-state lithium-ion batteries. In this work, a cubic phase garnet of nominal composition Li6.5Al0.25La2.92Zr2O12 is synthesized through a microwave-assisted solid-state route for the first time, reducing considerably the reaction times and heating temperatures. Lithium-ion diffusion behavior is investigated by electrochemical impedance spectroscopy (EIS) and state-of-art muon spin relaxation (mSR) spectroscopy, displaying activation energies of 0.55 0.03 eV and 0.19 0.01 eV respectively. This difference arises from the high inter-grain resistance, which contributes to the total resistance in EIS measurements. In contrast, mSR acts as a local probe providing insights on the order of the lattice, giving an estimated value of 4.6210􀀀11 cm2s􀀀1 for the lithium diffusion coefficient. These results demonstrate the potential of this lithium-stuffed garnet as a solid-state electrolyte for all-solid state lithium-ion batteries, an area of growing interest in the energy storage community.